Lower cowl scoop shape

Do you have any pics of the 13 row cooler installed on the rear baffle? I've thought about changing my own coolers but can't see how such a big opening in the rear baffle could work. How are your oil temps on a hot day? Why was the cooler changed and relocated from the nose bowl?

stewartb said:

Do you have any pics of the 13 row cooler installed on the rear baffle? I've thought about changing my own coolers but can't see how such a big opening in the rear baffle could work. How are your oil temps on a hot day?

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lets not talk about the oil cooler on the baffle ...... ah heck, why not, maybe some will learn from my mistakes..... so.....the story goes like this.

when we got the plane the baffles were terrible, badly made, gaps of over an inch square and we immediately struggled with temps from the moment we took her out of the container and put the wings on.... time pressure was on and we had a small window to ferry her up to Botswana, luckily it was the start of winter and temps were cool a cool 70ºF... so my plane partner flew her up and then grounded the plane till we had fixed the baffles.... I ordered a set of IO360 baffles from VANS and they arrived.....then the cowls came off and the baffle fitting began.....till now the oil cooler had been up front under cyl #2 and we were struggling with oil temps and with cyl #2 temps......so the old 10 row oil cooler came off with the old baffles, while the fitting of the back baffle plate was started the oil dipstick kept getting in the way so it got taken out and plugged with a temporary plastic plug..... this is about the time I arrived on the scene... and I got stuck in with gusto, we prepared the baffles, got them all built up and shaped and fiddled and faffed and then fiddled and then faffed....you all know how it goes. then one evening I was trying to figure out how we were going to do the oil cooler, I was walking around the engine (no cowls on) with the new 13 row cooler in my hand and found a wonderful spot behind cyl #3 where the oil cooler fitted in snugly between the baffle, cowl and engine mount......it was like it was MADE for a 13 row cooler..... so I suggested we put it there and all got busy busy busy and we fitted it..... then came the end of the project where you start figuring out what do to with the handful of left over nuts and bolts that were supposed to go into the project and what you had missed and it struck me that one of these items was the oil dipstick tube.....which now no longer fit in because there was a great big damn 13 row oil cooler in the way :evil:

but by now I had a serious case of "gottoflythisdamnplanerightnoworiamgonnadie" so we made a plan with a short oil dipstick that is a SON OF A beautiful old lady to use and check oil but hey.... it works for now..... end of story....

I have been quite happy with the oil temps since we have put this oil cooler in though, highest I have seen is 208 (at 105ºF OAT for a couple of hours flying) and normally when temps are around 95 oil temp will sit at around 190-195

remember though that we aren't able to lean much at these high temps because our CHT's then go over 400 which we dont like.

so we are considering 2 different options:
1. fit the oil cooler back below cyl#2, but about 4 inches lower than it was before and with a better opening scoop (before it was directly on the front skin of the cowl and we dont think it was getting clean airflow through).....but....even though we have a kit from BCSC for this it is going to be a mission as our starter motor is different to the BCSC IO390 starter so we will need to modify the brackets significantly. - also this puts the weight of the oil cooler up front which the REV2 doesn't like, it likes a light nose..
2. fit a carbon scoop where the oil cooler is currently that feeds into a 4" SCAT tube, this should allow the oil dipstick enough space to be fitted again, and mount the oil cooler on the firewall lower down where there is space.

both options have their challenges, I am worried that we won't get enough air through the 4" SCAT tube to maintain the oil temps we want.

here are some pics of our oil cooler behind cyl#3, note the re-inforcements on the back baffle to carry the cooler.

so its real easy for me to point a finger and say "but I wasn't there when they took the oil dipstick off" but I think its more important to learn from my mistake and learn to make sure that I FIRST take a look at all the parts when doing something and make sure I have a plan for ALL of the parts..... we live and learn

bodumatau said:

View attachment 46050

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That cooler is very close to the engine mount tube. Normal shaking of the engine could damage the engine mount and/or the oil cooler.

Take a look at my photos section...I have some diagrams on airflow optimization through an oil cooler. In support of those, I was told once that putting a one inch spacer between the baffle and the cooler helped performance. Try running a jet engine without a long inlet duct....

*that’s NOT to say that scat tubing is an efficient duct.....

http://www.supercub.org/photopost/search.php?searchid=10055

skywagon8a said:

That cooler is very close to the engine mount tube. Normal shaking of the engine could damage the engine mount and/or the oil cooler.

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It's just the angle of the photo, we have done about 60hrs since and it doesn't touch

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If CHTs are the focus? I'd lose that cooler, close the baffle, and put the cooler back on the nose with an outlet duct so it doesn't pressurize the lower cowl. I've got the opportunity to reduce cooler size or eliminate one of my nose mounted coolers right now but my new engine will make more heat so I'll probably leave things alone this go-round. I've dreamed up a few new cooler scenarios for my plane. Like a firewall mounted cooler fed by cowl ducts from the nose. Composite cowls would be easy to incorporate ducts into.

After a LOT of experimentation and measurement, the following things were the most effective at lowering chts.(67 cub, 150hp, @100smph 5500 ft msl. 2450 rpm.)
1. Ramps in front of cylinders, 20deg F ( to avoid raising front chts, drill 12-1/4 inch holes in each one.)
2. Boxing in the front of the engine to eliminate air leakage down the front of the engine, 27 deg F
3. Rear cowling lip, 10 deg F.
4. Deflection vane over #4, along with reducing the space behind #4, 20 deg F on #4.
5. Finding a binding rocker arm on #4, another 20 deg F.
Not effective: extending side cowl cheeks....(45 deg at 1.5 inches protrusion)
things I am trying: a half round (at least 3 inches diameter) on the bottom of the firewall. Incidentally, the two bottom cowl “vents” are good for 5 deg F each........ all this got me from 390F above ambient to 310F above ambient....fob

*note that these changes were measured sequentially, not separately.

slight deviation from the topic, but has anyone out there mounted their oil cooler to the lower cowling? (not to the engine but to the cowling directly), I have seen this done on a few ROTAX installations, they graft a scoop into the front of the cowl that can receive the oil cooler, your flexible oil pipes must be long enough to take up vibration and movement, the oil cooler is held into the receptacle by a set of bungee cords, so when you drop your lower cowl you unhook your bungees and your oil cooler hangs on its flexible oil pipes, or you put a bungee in place that hangs it on an induction tube or something while it is out of it cowl mount, just so it doesn't hang down too much.

bodumatau said:

slight deviation from the topic, but has anyone out there mounted their oil cooler to the lower cowling? (not to the engine but to the cowling directly), I have seen this done on a few ROTAX installations, they graft a scoop into the front of the cowl that can receive the oil cooler, your flexible oil pipes must be long enough to take up vibration and movement, the oil cooler is held into the receptacle by a set of bungee cords, so when you drop your lower cowl you unhook your bungees and your oil cooler hangs on its flexible oil pipes, or you put a bungee in place that hangs it on an induction tube or something while it is out of it cowl mount, just so it doesn't hang down too much.

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yes, see the wildcat thread...

fobjob said:

Take a look at my photos section...I have some diagrams on airflow optimization through an oil cooler. In support of those, I was told once that putting a one inch spacer between the baffle and the cooler helped performance. Try running a jet engine without a long inlet duct....

*that’s NOT to say that scat tubing is an efficient duct.....

http://www.supercub.org/photopost/search.php?searchid=10055

Click to expand...

Made some quick sketches based on your ideas in the picture gallery to fit my current oil cooler to try clean up the air flow to oil cooler and cyl#3, tell me if I am on the right track



the above sketch would be to fit into this space.

bodumatau said:

View attachment 46052

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Bend that new top baffle up about 30 or so degrees. Extend it to the cowl with an anti chafe seal against the cowl.This will help to smoothly direct the air into the cooler.

I agree with skywagon. The problem remains with the bottom of the cooler. It is probably getting too much heated air...Avoid any sudden angles in your deflection baffles. If you could move the cooler rearward, things would be easier. The top baffle as described might also improve CHT on #3.

*but, since you said that your oil temps were under control in post #32, try the top deflector for the possible improvement in CHT. You might even partially block off the bottom of the cooler to eliminate hotter air flow through the cooler and increase the flow on the back side of #3.....

fobjob said:

After a LOT of experimentation and measurement, the following things were the most effective at lowering chts.(67 cub, 150hp, @100smph 5500 ft msl. 2450 rpm.)
1. Ramps in front of cylinders, 20deg F ( to avoid raising front chts, drill 12-1/4 inch holes in each one.)
2. Boxing in the front of the engine to eliminate air leakage down the front of the engine, 27 deg F
3. Rear cowling lip, 10 deg F.
4. Deflection vane over #4, along with reducing the space behind #4, 20 deg F on #4.
5. Finding a binding rocker arm on #4, another 20 deg F.
Not effective: extending side cowl cheeks....(45 deg at 1.5 inches protrusion)
things I am trying: a half round (at least 3 inches diameter) on the bottom of the firewall. Incidentally, the two bottom cowl “vents” are good for 5 deg F each........ all this got me from 390F above ambient to 310F above ambient....fob

*note that these changes were measured sequentially, not separately.

Click to expand...

Just curious:

Could you elaborate on your deflection vane for #4? Deflecting air from the side of the cowl, or the top down to #4?

Also, how did you end up find the binding rocker arm?

you guys are only looking at 1/2 of the equation (only pushing air through cooler).....

if you SUCK air through it, then it's less important if the air is clean entering cooler....

but yes, a baffle to above the cylinder in his installation would help prevent using that hot air directly off cylinder fins in lower cooler...

I agree with Mike. Impedance matching on the input and output of heat exchangers is important. Having said that, I’m toying with an exit air matching horn on the outlet of the #4 cooling air. The geometry is complex, but I’m futzing around with it. It’s hard to get too motivated, since I’ve hit all of the low hanging fruit for easy cooling measures. It could always use more, though....
I was taking the rocker arms off, looking to see if the oil squirt hole was plugged or missing. The split pin bushing was pushed off center, rubbing hard against the metal boss the pivot pin went into. I centered it as a matter of course, and noticed on my next flight a mysterious drop in the CHT. My mechanic had changed two (#4) cylinders and didn’t think to do that, so the problem got moved from old cylinder to new cylinder.....twice..the deflection vane goes from the top of the cowl to the bottom of the rear of #4, mounted on the motor end by that threaded (1/4-20) boss between #2 and #4....tried the same thing on #3, but it didn’t work well, the geometry is different. No pics, it’s dark in there....

bodumatau said:

thanks Fobjob, we have, subsequent to the photos above, put a vertical fence up the front of #1
View attachment 46043
roughly the size of the red rectangle, this brought #1 temp in line with #4

then we cut off the stiffener in front of #2 and replaced it with another underneath
View attachment 46044
roughly where the red line is and this brought #2 in line with #1 & #4

we still have about 20ºF higher temps on #3 throughout the operating range, but I must add that we have our 13 row oil cooler behind #3 stealing air from that back corner.

we will try the ramp in front of #1 and let you know how it goes.

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Are you having high oil temp, high #3 CHT, or both?

Here's how I moved my oil cooler, which had previously been mounted behind #4: https://www.supercub.org/forum/show...ature-question&p=739392&viewfull=1#post739392

I'm willing to bet that adding a baffle between the oil cooler and #3 (similar to what I put here: https://www.supercub.org/forum/show...ature-question&p=739404&viewfull=1#post739404) would help both #3 CHT and oil temps.

You also need to pay attention to the fin depth on the back side of #3 on a Lycoming. If you add a baffle between the oil cooler and #3, you need to make sure it allows air past the shallow fins. More information here: http://www.vansairforce.com/community/showthread.php?t=37835

CamTom12 said:

Are you having high oil temp, high #3 CHT, or both?

Here's how I moved my oil cooler, which had previously been mounted behind #4: https://www.supercub.org/forum/show...ature-question&p=739392&viewfull=1#post739392

I'm willing to bet that adding a baffle between the oil cooler and #3 (similar to what I put here: https://www.supercub.org/forum/show...ature-question&p=739404&viewfull=1#post739404) would help both #3 CHT and oil temps.

You also need to pay attention to the fin depth on the back side of #3 on a Lycoming. If you add a baffle between the oil cooler and #3, you need to make sure it allows air past the shallow fins. More information here: http://www.vansairforce.com/community/showthread.php?t=37835

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we are happy with our oil temp right now - we did try tape up the bottom third of the oil cooler to feed more air to #3 but that didn't change #3 CHT's and it pushed up the oil temps by 25ºF to 215º.

we would like to see 20ºF less CHT on #3.

we have a nice gap at the back of #3 to let air down to the lower quadrant of #3

I have been toying with your idea of moving the oil cooler down onto the firewall with a scat tube feeding it, just havent built up the courage to do it....

Can you get a more top-down angled pic of #3? Maybe even one from as much of an angled forward image as you can grab and still see the fins on the backside of #3?

I moved my oil cooler to lower my oil temps (big success there). Since your OTs are fine, I’d try some other things first that might be more “outpatient” level of involvement before you crack open your baffles again to move that oil cooler.

For your #3, I’d try to build some airflow guides to fit over the cylinder, in front of the oil cooler. I’d do it like the guy does here:


source: http://www.ez.org/canardpages/pages/waynehicks/chapter_23_7.htm

Make sure that the airflow guides “stand off” the shallow fins on the back of the #3. I’d use this thread as a resource: http://www.vansairforce.com/community/showthread.php?t=37835

Fins in open air aren’t necessarily getting airflow through them. If there are fins that don’t tie directly into a path to lower pressure (the lower cowl space), I think you’re not using all the cooling potential on the table. Building an “airflow guide” should be pretty easy to do. And if you’ve got a lot of space back there, they could be temporarily attached for a quick flight test.

EDIT: I just read through your other thread about the fuel injection system - my comments below have already been covered there by more experienced folks.

————————————

Also, since this is an IO, I’m a little out of my experience level, but I just fixed my induction tubes leaks and that really helped bring my cruise CHTs down (on a carb’d motor). May not be as big of a deal for an IO. I used an O-ring set up from the folks that make the SDS EFI (http://sdsefi.com/sdsaero.htm).

Are your high CHTs only in cruise? Or also in climb out? Might be a plugged Or dirty injector line or tip or something like that?

stewartb said:

If CHTs are the focus? I'd lose that cooler, close the baffle, and put the cooler back on the nose with an outlet duct so it doesn't pressurize the lower cowl. I've got the opportunity to reduce cooler size or eliminate one of my nose mounted coolers right now but my new engine will make more heat so I'll probably leave things alone this go-round. I've dreamed up a few new cooler scenarios for my plane. Like a firewall mounted cooler fed by cowl ducts from the nose. Composite cowls would be easy to incorporate ducts into.

Click to expand...

this is definitely on the agenda, just trying to find the best way to mount the oil cooler, I am not a fan of hanging it on some aluminium angle iron especially if you need to hang it 5 inches below the engine, just too much leverage on the angle iron.... so considering grafting it into the lower cowl like you have done Stewart.

after some test flying we saw that the right exhaust branch is clearly leaner than the left, right side is cyl#3 & 4, left side is cyl#1 & 2.

with #3 running on average 25ºF hotter than the others we assume it is #3 blowing white here, we have changed out the fuel injection nozzle and still the same. what could be the cause? some are saying it can't be an induction leak cause that only affects carburettor engine?
- sticky rocker or valve intake side and you would loose power but not run lean - you would run overreach cause you can't get the air into the cylinder?
- sticky rocker or valve on exhaust would mean high EGT's which we dont have?
- fuel nozzles are all same
what else could it be? - maybe my cold induction box just somehow feeds a lot of air to #3? is this possible?

we have done the fuel flow test into cups, we get very close flows across all 4 cylinders, did the test twice, get the same result.

Piper pa 25 pawnee. If it will cool a spray plane working the design should cool a cub


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some work done tonight, put a scoop on the oil cooler and #3

not enough time to finish the top scoop for the oil cooler, test flying tomorrow morning to see if this is a step in the right direction.

What fuel injection system do you have? Yes an intake leak can cause a problem depending on the system. I would expect temps to be different for each cylinder if all nozzles are the same. Cylinder air filling depends on several factors intake runner length/size/bends, valve overlap, RPM. Gami injectors adjust for each cylinder. I would say you need more fuel to #3
DENNY

DENNY said:

What fuel injection system do you have? Yes an intake leak can cause a problem depending on the system. I would expect temps to be different for each cylinder if all nozzles are the same. Cylinder air filling depends on several factors intake runner length/size/bends, valve overlap, RPM. Gami injectors adjust for each cylinder. I would say you need more fuel to #3
DENNY

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a Bendix RSa5, we are looking at changing the fuel flow to #3 slightly

Here is how I have fabricated the bottom cooling lip. Posterboard and tape to make the pattern/shape.

Steve Pierce said:

Here is how I have fabricated the bottom cooling lip. Posterboard and tape to make the pattern/shape.

View attachment 46070

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after finishing that bottom cooling lip you were WELL PRACTICED at riveting :lol:8)
looks awesome

Notice the two metal "side curtains" Bellanca added to the boot cowl channel. I assume that helps smoothly direct exit air flow by reducing the chance of turbulent air entering that area from the sides

Gary[/QUOTE]





I have never noticed the " side curtains " before. Thank you for pointing that out. It would be neat to hook up a manometer inside the cowling and see how the pressure is effected with them removed.

Jonny

bodumatau said:

thanks Fobjob, we have, subsequent to the photos above, put a vertical fence up the front of #1
View attachment 46043
roughly the size of the red rectangle, this brought #1 temp in line with #4

then we cut off the stiffener in front of #2 and replaced it with another underneath
View attachment 46044
roughly where the red line is and this brought #2 in line with #1 & #4

we still have about 20ºF higher temps on #3 throughout the operating range, but I must add that we have our 13 row oil cooler behind #3 stealing air from that back corner.

we will try the ramp in front of #1 and let you know how it goes.

Click to expand...

I took a brand new 4 way, digital CHT set and stuck them through the top of a closed, 5 gallon metal can, with a pin hole vent. I put the can on the stove and brought it up to 200 degrees. I turned off the stove and let things stabilize for a few minutes. 2 readings were 9 degrees apart and the others were around 5. I think it's great that so much quality work is going into this, but just because it's digital doesn't mean it's perfect. For me, 20 degrees is zero.

Jonny

We went thorugh all these same problems with our banner tow Huskies. When you rob air from the cylinders to run it through an aft mounted oil cooler you heat up the cylinders, which then heat the oil. No problem in regular service. Aft coolers are neat and clean, but in extreme cases, you might consider just mounting the cooler under the firewall like so many Restiicted Category banner planes.

I have couple of Harrison GPU coolers which used to be the standard for south Florida banner ops. Makes anything run cool in high temps. Seal up you rear baffle, fix up a generous cooling lip and you're on your way.

If you are curious pm me and I'll send you a foto. I paid very little for the coolers, and I'll gladly pass it onto you. It worked great for us for years.

Replacing my front mounted Harrison with a drop-in replacement Niagra Cub Cooler eliminated all oil temp issues.....